An apparatus is disclosed that provides an estimate of the semiconductor junction
temperature of a semiconductor device as a function of the electrical current flowing
across the corresponding semiconductor junction. The apparatus includes a current
sensor that samples and measures the current flowing across the semiconductor junction
and provides an output signal indicative of the measured value to a current-to-temperature
converter. The current-to-temperature converter estimates the temperature of the
semiconductor junction using equations that include constants empirically derived
for the particular device configuration including cooling and mounting methods
used with it. The current-to-temperature converter provides an output temperature
signal that is compared to a predetermined temperature threshold value, and in
the event that the output temperature signal exceeds the predetermined temperature
threshold value, an alarm signal is set.
